There is evidence for a deleterious effect of maternal mental illness on motherinfant interaction. Presence of mental illness and lowered maternal cognitive function independently predict quality of interaction, but their combined effect on interaction is unclear. A pilot study was conducted to explore the relationship between maternal serious mental illness (SMI), cognitive function, and mother-infant interaction. Six mothers with SMI (two with schizophrenia and four with depression) and 12 mothers with no psychiatric history were recruited, together with their infants (all aged between 5 and 18 weeks). Mother-infant